Blech effect in dual damascene copper-low k interconnects

The electromigration threshold in copper interconnect is reported in this study. The critical product jLc was first determined for copper-oxide interconnects in the temperature range 250°C-350°C from package level experiments. It is shown that the product does not significantly change in this temperature range. Then jLc was extracted for copper-low k dielectric (k=2.8) interconnects at 350°C. A larger value than for oxide dielectric was found. Finally, a correlation between n values from Black´s model and jL conditions was established for both dielectrics.